The present invention relates to a pusher device for positioning the ends of plastic optical fibers, and more particularly to a pusher device employable for a multiple-core optical fiber cable incorporating plural plastic optical fibers.
FIG. 3 shows a pusher device employed for a dual-core optical fiber cable in the priot art. As shown in FIG. 3, an optical fiber cable 1 is constituted of two plastic optical fibers 2 and 3 having different flows, sheaths 4 and 5 made of polyethylene, etc. for covering the respective optical fibers 2 and 3, and an outer cover 6 made of polyvinyl chlordie etc. for generally covering the sheats 4 and 5. The sheaths 4 and 5 are exposed at the end portion of the optical fiber cable 1, and are held by a pair of pusher members 8 and 9 of a pusher device 7 at a predetermined position to enhance a frictional force between the optical fiber 2 and the sheath 4 and a frictional force between the optical fiber 3 and the sheath 5, thus positioning the ends of the optical fibers 2 and 3. The optical fibers 2 and 3 are projected from the end surfaces of the sheaths 4 and 5 by a predetermined amount. The end surfaces 2a and 3a of the optical fibers 2 and 3 are arranged in opposed relation with an optical connector (not shown) so as to transmit an optical signal.
However, the conventional pusher device 7 is designed such that each of the sheaths 4 and 5 is held in a single position, and when a clamping force of the pusher members 8 and 9 is increased so as to securely prevent slip of the optical fibers 2 and 3 relative to the sheaths 4 and 5, local stress concentration is generated to remarkably reduce light transmittance of the optical fibers 2 and 3. To cope with this problem, the clamping force of the pusher members 8 and 9 must be supporessed to some degree, but in this case, the end portions of the optical fibers 2 and 3 are liable to slip in the sheaths 4 and 5. As a result, when the optical fiber 1 is bent near the end portion thereof as shown in FIG. 3, the end surfaces 2a and 3a of both the optical fibers 2 and 3 are slipped from a predetermined position because of difference in curvature. For example, the end surface 2a of the optical fiber 2 on the side of smaller curvature in FIG. 3 is projected from the predetermined position, and is brought into abutment against the optical connector (not shown) to cause a serious accident such as damage of the end surfaces.